Captive, pelagic red crabs (Pleuroncodes planipes) had shortened lifespans and cutaneous black spots. Histologically, epidermal and mesenchymal cells had 3-5 µm diameter intranuclear inclusions, necrosis, vacuolation, and/or hyperplasia. The remaining organs were histologically unremarkable. Ultrastructurally, nuclei contained rod-shaped, 70-100nmx250-350 nm virions with a double membrane. PCR on 32 animals was negative for WSSV, and suggestive of a novel virus. The genomic sequence of the virus could not be retrieved due to the low amount of DNA obtained from the paraffin embedded tissue. This is consistent with a novel viral infection, and is the first description of a viral disease in pelagic red crabs.